The present invention relates to scanned probe microscopy (SPM), and more specifically, to a SPM probe having a tip projecting from a crystal facet surface.
Atomic force microscopy (AFM) is a branch of SPM that creates images of sample surfaces (e.g., the surface of a semiconductor device) using an AFM probe. AFM probes include a cantilever beam and a tip extending from the cantilever beam. The tip is a relatively thin rod or nanowire. The tip of the cantilever beam may be used to image high aspect features (e.g., trenches or wells) located along a sample surface. A high aspect feature generally has a relatively narrow and deep. The depth that an AFM probe may reach into a deep feature depends on the angle or orientation of the tip relative to the sample surface. If the tip is oriented generally perpendicular to the sample surface, this typically allows for the tip to reach into the deepest portions of the feature. However, the cantilever beam is usually positioned at an angle relative to the sample surface. Thus, the tip is also positioned at an angle relative to the sample surface. As a result, sometimes the tip may not be able to reach into the deepest portions of the features.
In one approach, the AFM probe may be tilt corrected for high aspect ratio probing, where the angle of the cantilever beam relative to the sample surface is adjusted. In another approach, tips having a relatively high aspect ratio are provided. These high aspect ratio tips may be, for example, carbon nanotubes (CNT) tips, carbon fiber tips, and focus ion beam (FIB) milled tips. However, these tips are limited in manufacturability and are relatively costly to fabricate. FIB milled tips may be shaped and oriented at a specific angle. However, the amount of angling of the FIB milled tip with respect to the cantilever beam may be limited by material constraints as well as FIB milling effects such as re-deposition.